In many fields that employ polymers it may be desirable to tag or mark such polymers to facilitate monitoring thereof. By the term "monitoring" is meant herein any type of tracing or tracking to determine the location or route of the polymers, and any type of determination of the concentration or amount of the polymer at any given site, including singular or intermittent or continuous monitoring. For instance, it may be desirable to monitor water treatment polymers in water systems, particularly industrial water systems, or to monitor polymers that may be present in waste fluids before disposal, particularly industrial waste fluids, or to monitor the polymer used for down-hole oil well applications, particularly the route taken after introduction down-hole, or to monitor polymers that may be present in fluids used to wash a manufactured product, for instance a polymer-coated product, to determine the amount of polymer washed or leached therefrom. By fluids or liquids as used herein generally is meant aqueous, non-aqueous, and mixed aqueous/non-aqueous fluid systems. As seen from the above list of possible applications of polymer monitoring, the purpose of such monitoring may be to trace or track or determine the level of the polymer itself, or to trace or track or determine the level of some substance in association with the polymer, or to determine some property of the polymer or substance in association with the polymer, for instance its leachability.
Conventional techniques for monitoring polymers are generally time-consuming and labor intensive, and often require the use of bulky and/or costly equipment. Most conventional polymer analysis techniques require the preparation of calibration curves for each type of polymer employed, which is time-consuming and laborious, particularly when a large variety of polymer chemistries are being employed, and the originally prepared calibration curves lose their accuracy if the polymer structures change, for instance an acrylic acid ester mer unit being hydrolyzed to an acrylic acid mer unit. Direct methods wherein the level of functional groups present in a polymer is determined analytically are generally not practical for industrial use, particularly when it is desired to monitor a polymer on a frequent or continuous basis, or when rapid monitoring results are needed. Indirect methods of polymer monitoring may provide more rapid results using simpler techniques, but in many instances faster and/or more accurate determinations are desirable.
Polymers tagged with pendant fluorescent groups are generally easily monitored, even when present at low concentrations. In theory, the fluorescence quantum efficiency and molar extinction coefficient of the fluorescent group need only be large enough to generate an acceptable signal to noise ratio for the tagged polymer in the matrix in which detection occurs. What is required in terms of quantum efficiency and molar extinction to detect fluorescently tagged polymer will depend upon background fluorescence of the matrix at the wavelength that emission is being monitored, the intensity of the excitation source, and the efficiency of the emission collection device (detector). In practice, the incorporation of a fluorescent species in a polymer in the amount of one weight percent or less is desirable; this should be sufficient to permit the detection of polymer at ppm or ppb concentration levels, provided the fluorescent quantum yield and the light absorbance molar extinction coefficient of the fluorescent tagging agent are not significantly adversely affected by its attachment to the polymer.
Some polymers tagged with pendant fluorescent groups are known. A process for preparing a cross-linkable fluorescent compound bonded polymer from the copolymerization of a fluorescent compound wherein an acrylamide moiety and the aromatic fluorescing moiety are directly linked through an amide bond to the aromatic ring is disclosed in Japanese Patent No. 1,141,147. Other fluorescent acrylamide based polymers are disclosed in U.S. Pat. Nos. 5,043,406 and 4,999,456. Polymers tagged with pendant fluorescent groups have been prepared by the transamidation derivatization of the pre-existing polymers having carbonyl-type pendant groups in U.S. Pat. No. 5,128,419. Another post-polymerization modification of a polyacrylamide with a fluorescing moiety is disclosed in U.S. Pat. No. 4,813,973. The preparation of certain vinylic coumarin derivatives is disclosed in Collection Czechoslov. Chem Common, Vol. 45, 1980, pgs. 727-731. However, none of these disclosures cite the monomers and polymers of the instant invention.
A specific example of the utility of a polymer tagged with pendant fluorescent groups may be drawn from the field of solids/liquid separation.
In the water treatment field of solids/liquid separation, suspended solids are removed from water by a variety of processes, including without limitation, sedimentation, straining, flotation, filtration, coagulation, flocculation, emulsion breaking and the like. Additionally, after suspended solids are removed from the water they must often be dewatered so that they may be further treated or properly disposed. Liquids treated for solids removal often have as little as several parts per billion of suspended solids or dispersed oils may contain large amounts of suspended solids or oils. Solids being dewatered may contain anywhere from 0.25 weight percent solids, to 40 or 50 weight percent solids material. So called liquid solids separation processes are designed to remove solids from water, or, conversely and depending upon the desired component, liquids from solids.
While strictly mechanical means have been used to effect solids/liquid separation, modem methods often rely on mechanical separation techniques which are augmented by synthetic and natural cationic polymeric materials to accelerate the rate at which solids can be removed from water. These processes include treatment of raw water with cationic coagulant polymers which settle suspended inorganic particulates and make the water usable for industrial or municipal purposes. Other examples of these processes include the removal of colored soluble species from paper mill effluent wastes, the use of organic flocculant polymers to flocculate industrial and municipal waste materials, recovering a sludge and emulsion breaking.
Regarding the mechanism of separation processes, particles in nature have either a cationic or anionic charge. Accordingly, these particles often are removed by a water soluble coagulant or flocculent polymer having a charge opposite to that of the particles. This is referred to as polyelectrolyte enhanced liquid/solids separation processes, wherein a water soluble or dispersible ionically charged polymer is added to neutralize the charged particles or emulsion droplets to be separated. The dosage of these polymers is critical to the performance of the process. Too little ionically charged polymer, and the suspended particles will not be charge neutralized and will thus still repel each other. Too much polymer, and the polymer will be wasted, or worse, flocculation will be adversely affected.
If the polyelectrolyte or ionically charged polymer being added is very effective for the given process, the polyelectrolyte that leaves with the water fraction generally represents an overdosage. More polyelectrolyte was added than required. If the polyelectrolyte being added is not very effective for the given process, significant amounts of polymer may leave the process with the water fraction as an indication of the polymers performance deficiencies. In either instance, a determination of the amount of polyelectrolyte that leaves a separation process with the filtrate or water fraction would be extremely beneficial. An effective polyelectrolyte should be added to a separation process in an amount just at or above that consumed by attachment to the solids or oil surfaces. Whether the dosage selected approaches this optimal dosage could be determined, and the dosage adjusted if necessary, if the level of the polyelectrolyte in the filtrate could be easily monitored. A less effective polyelectrolyte could be readily detected, and the polyelectrolyte selection changed if the level of the polyelectrolyte in the filtrate could be easily monitored.
Monitoring the concentration of polyelectrolyte in the filtrate is a formidable task not well suited to industrial applications. Analytical techniques such as colloid titration are complicated and time consuming and do not permit a real time result. Electronic instrumentation to determine charge is available, but such devices are expensive, and do not differentiate between charge associated with a polymer, or charge from other sources, including the water, solids, or other constituent in the effluent. Time consuming measurements are inefficient since the characteristics of a waste stream or emission may vary considerably with time.
The use of fluorescence emission spectroscopy to determine the concentration of a fluorescent chemical species is extremely rapid and sensitive, but the species being monitored must be fluorescent. A typical polyelectrolyte is not fluorescent or is not sufficiently fluorescent for monitoring by emission spectroscopy. Since the polyelectrolyte in its performance is consumed in the sense that it attaches to the solids and/or oils and is separated from the water therewith, adding a fluorescent signature chemical or tracer that follows the water would not reveal what fraction of the polyelectrolyte has been consumed, even if the concentration of the tracer can be correlated to polyelectrolyte dosage.
While determining polyelectrolyte dosage, for instance by adding a tracer in known proportion to the polyelectrolyte and monitoring the tracer concentration to determine if the target dosage or feed rate is being met, may in and of itself be of significant assistance, a water-soluble totally inert tracer is an indicator of only the theoretical zero-consumption concentration of the polyelectrolyte in the filtrate, and not the actual filtrate concentration of the polyelectrolyte. A signature chemical or tracer that itself preferentially follows the solids and/or oil likewise is not an indicator of polyelectrolyte consumption and hence polyelectrolyte performance.
It is therefore an object of this invention to provide a process for monitoring a polyelectrolyte water treatment chemical that is consumed in its performance, preferentially associating with one phase in a multiphase system.
It is an object of the present invention to monitor a polyelectrolyte that preferentially associates with one phase of a multiphase system by determining the extent of such preferential association.
It is an object of the present invention to determine the extent of preferential phase association of polyelectrolyte in a multiphase system using a technique that is rapid and sensitive. It is an object of the present invention to determine the extent of preferential phase association of a polyelectrolyte in a multiphase system using a technique that can be employed on a semi-continuous or continuous basis.
It is an object of the present invention to determine the extent of preferential phase association of a polyelectrolyte in a multiphase system using a technique that can be employed on line. It is an object of the present invention to determine the extent of preferential phase association of a polyelectrolyte in a multiphase system using a technique that determines the concentration of the polyelectrolyte in the non-preferred phase. These and other objects of the present invention are described in detail below.
The ability to exploit fluorescent polymers and to obtain economic benefits from their deployment depends upon the ability to detect fluorescence contributed by the polymer over any background incidental to the application. If this necessary condition can be achieved, and the increase in observed fluorescence as a finction of polymer dose corresponds to optimal product performance, then a useful tool has been developed. These and other objects are provided by the present invention which is described in more detail below.